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## Chapter 7: Cellular Respiration - Working out has tremendous benefits to our health: - Enhances our ability to take in oxygen and deliver it to our muscles - Greater lung capacity, more red blood cells, greater blood supply to our brains, stronger heart - **Autotrophs** create their own...

## Chapter 7: Cellular Respiration - Working out has tremendous benefits to our health: - Enhances our ability to take in oxygen and deliver it to our muscles - Greater lung capacity, more red blood cells, greater blood supply to our brains, stronger heart - **Autotrophs** create their own food - **Heterotrophs** have to eat their food - Energy flows into an ecosystem as sunlight and leaves as heat - Photosynthesis generates $O_2$ and organic molecules, which are used in cellular respiration - All living cells use chemical energy stored in organic molecules to produce ATP, which powers work. - Several processes are central to cellular respiration and related pathways. - The breakdown of organic molecules is exergonic - Fermentation is a partial degradation of sugars that occur without $O_2$ - Aerobic respiration consumes organic molecules and $O_2$ and yields ATP - Anaerobic respiration is similar to aerobic respiration but consumes compounds other than $O_2$ - Cellular respiration - the many-stepped reaction that breaks carbohydrates, proteins, and lipids down to release the energy stored in their chemical bonds, producing ATP: - Glucose + oxygen - carbon dioxide + water + ATP - $C_6H_{12}O_6$ + $6O_2$ - $6CO_2$ + $6H_2O$ + 38ATP + heat - Glucose, fats & proteins are oxidized as they lose hydrogen to produce carbon dioxide - Oxygen is reduced as it gains hydrogen to produce water - Only 40% efficient at capturing energy released as ATP. The rest is lost as heat and contributes greatly to producing and maintaining body heat. - The high-energy electrons removed from glucose are accepted by either NAD+ (nicotinamide adenine dinucleotide) or FAD+ (flavin adenine dinucleotide) and carried to the electron transport system and finally bond to oxygen at the end to make water after their energy has been harvested into ATP - NAD and FAD are co-enzymes as they help cellular respiration reaction to occur - **Chemical reactions** that transfer electrons between reactants are called oxidation-reduction reactions, **or redox reactions** - In oxidation, a substance loses electrons, or is oxidized - In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced) - "OIL RIG" - oxidation is loss, reduction is gain - The electron donor is called the **reducing agent**. - The electron receptor is called the **oxidizing agent** - Some redox reactions do not transfer electrons but change the electron sharing in covalent bonds. - During cellular respiration, the fuel (such as glucose) is oxidized, and $O_2$ is reduced. ### There are four main steps in cellular respiration: 1. **Glycolysis** in cytoplasm - Splitting of 6C glucose into 2 3C pyruvate molecules requires 2ATP to occur. - In the process of making pyruvate, 4ATP, NADH, and FADH2 are produced, so there is a net gain of 2ATP per glucose molecule. - Occurs in the cytoplasm of cells. 2. **Transition reaction** in mitochondria. - Both 3C pyruvate are oxidized to two 2C acetyl CoA molecules and 2 carbon dioxide molecules. - Occurs in the matrix (central, fluid filled portion) of the mitochondria. 3. **The Citric Acid (TCA) cycle (Kreb's Cycle)** - Cyclic series of reactions that take each 2C acetyl CoA molecule and produce 2 carbon dioxide and 2 ATP molecules per acetyl CoA molecule. - Requires multiple enzymes. - TCA turns twice per glucose molecule as 2 acetyl CoA are produced for each glucose. - Occurs in the matrix (central, fluid filled portion) of the mitochondria. 4. **Electron transport chain** only works if oxygen is present. - Series of carrier chemicals that accept glucose's high energy electrons from NADH and FADH2. - 90% of ATP is generated in this step. - As electrons travel through series, they change from high energy to low energy. - Energy is harvested in 32 or 34 ATP. - Oxygen is the final electron acceptor, forming water. - Occurs in the cristae (folds of the inner membrane) of the mitochondra.